fix(jira-dashboard): Fix release issues

[GLundh]

When the new frontend support was added, the introduced exports- field in jira-dashboards package.json breaks for Node <21.

Let's just use Node 21.

Checklist before requesting a review

• [X] I have performed a self-review of my own code
• [X] I have verified that the code builds perfectly fine on my local system
• [X] I have verified that my code follows the style already available in the repository
• [X] A changeset describing the change and affected packages. (more info)
• [ ] Added or updated documentation
• [ ] Tests for new functionality and regression tests for bug fixes
• [ ] Screenshots attached (for UI changes)

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: dac145b5db5184283982c539add8c404faf088de

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

| Name | Type | | ------------------------------------- | ----- | | @axis-backstage/plugin-jira-dashboard | Patch | | app | Patch | | backend | Patch |

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